CONSTRAINTS ON THE GENESIS OF CASSITERITE DEPOSITS IN MAYO-DARLÉ, CAMEROON: INSIGHTS FROM INTRUSION-RELATED TO HYDROTHERMAL DEPOSIT

The global supply of tin, as well as a notable portion of tungsten resources, is largely sourced from Sn-W vein and greisen deposits, which are formed through complex magmatic-hydrothermal systems. The genesis of these deposits is a product of interactions between magmatic activity and hydrothermal processes that effectively mobilize and concentrate mineralizing fluids. This research is dedicated to enhancing our understanding of the geological and hydrothermal dynamics that drive the accumulation of metals and the development of such deposits. Our approach to this is multidisciplinary, integrating (i) extensive field investigations, (ii) optical petrography, (iii) whole-rock geochemical analyses (XRF, ICP-MS, SEM, EPMA), micro-Raman spectroscopy, laser-ablation ICP-MS, and cassiterite u-pb geochronology. These techniques collectively provide a comprehensive map of texture, mineralogy, major and trace-element chemistry and ages at the individual mineral scale. The focus of our study is the Lower Eocene Sn-deposit located in Mayo-Darlé, northwest Cameroon, which is a reference site for examining the magmatic and hydrothermal processes that culminate in the formation of such deposits.

The deposit originated from magmatic-hydrothermal or hydrogenic metal-rich systems, deposited in conjunction with Late Cenozoic intraplate calc-alkaline felsic magmatism and characterized by greisenization. Within this region, tin mineralization occurs in various forms—massive, veined, stockwork, and disseminated—within highly fractionated granites, associated with minerals such as bastnaesite (Bsn-Ce), columbite (Clb-Fe), and fluorite (Fl). Petrographic analyses reveal that greisens are either rich or devoid of cassiterite, while stockworks and veins are uniformly mineralized. The mineralogical composition recorded are Qtz+Cst+Mus+Bt+Fl+Rt+Pl for the cassiterite-bearing greisen; Qtz+Mus+Tour+Chl for the barren greisen, Qtz+Mus+Cst+Tour+Chl for the veins and stockworks. This investigation underscores the critical interplay between magmatism, the evolution of permeability, and hydrothermal alterations as these factors collectively play pivotal roles in enhancing the mineralizing fluids migration, thereby facilitating the formation of extensive hydrothermal deposits.